A. Technical Field
The present invention relates to a production process for a hydroxyalkyl ester which comprises the step of carrying out a reaction between a carboxylic acid and an alkylene oxide.
B. Background Art
As to production processes for a hydroxyalkyl ester which comprises the step of carrying out a reaction between a carboxylic acid and an alkylene oxide, conventional ones have problems in respect to conversion or selectivity in the reaction, for example, in that they involve the formation of by-products such as alkylene glycol dicarboxylates and dialkylene glycol monocarboxylates. Thus, various studies are made to enhance the conversion or selectivity in the reaction.
For example, it is known that if the alkylene oxide is supplied to a reactor in a molar quantity excessive to (meth)acrylic acid, then the formation of the by-products is inhibited, with the result that the conversion or selectivity in the reaction is enhanced (e.g. JP-B-013019/1966, JP-B018890/1968). In addition, JP-B-006182/1989 discloses a process in which metaboric acid is used jointly with a chromium catalyst to enhance the selectivity in the reaction, and JP-A-133227/1976 discloses a process in which the reaction is carried out in the presence of a protonic acid having a boiling point higher than that of the aimed ester, and JP-A-027945/1986 discloses a process in which the reaction is carried out with a trivalent chromium compound used as a catalyst in a manner such that the wavelength which exhibits the maximum absorbance in the wavelength range of not less than 500 nm in a visible absorption spectrum of the reaction liquid can be more than 575 nm at the end of the reaction.
However, the enhancement of the conversion or selectivity in the reaction by these conventional processes cannot be said to be sufficient.
A. Object of the Invention
An object of the present invention is to provide a production process for a hydroxyalkyl ester which comprises the step of carrying out a reaction between a carboxylic acid and an alkylene oxide, wherein the production process can sufficiently enhance the conversion or selectivity in the reaction.
B. Disclosure of the Invention
The present inventors diligently studied to solve the above problems. As a result, they completed the present invention by finding that if not the ratio between the carboxylic acid and the alkylene oxide as charged as raw materials, but the molar concentrations of the carboxylic acid and the alkylene oxide in the actual reaction liquid were controlled so as to satisfy a certain relationship throughout the reaction, then the selectivity in the reaction would sufficiently be enhanced, and further, the conversion in the reaction would also be enhanced.
That is to say, a production process for a hydroxyalkyl ester, according to the present invention, comprises the step of carrying out a reaction between a carboxylic acid and an alkylene oxide in the presence of a catalyst, with the production process being characterized in that the reaction is carried out in a reaction liquid under conditions where a relationship a less than b is kept throughout the reaction wherein xe2x80x9caxe2x80x9d is a molar concentration (mol %) of the carboxylic acid in the reaction liquid and wherein xe2x80x9cbxe2x80x9d is a molar concentration (mol %) of the alkylene oxide in the reaction liquid.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.